Preliminary study of a composite process in concrete manufacture

Wu, Xiaofu; Li, Dongxu; Qinghan, Bian; Guo, Liqun; Ming-shu, Tang

doi:10.1016/0008-8846(87)90033-0

Cited by 18 publications

(8 citation statements)

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“…The quality of interfacial zone depends on surface characteristics of the aggregate particles, the degree of bleeding, chemical bonding and the specimen preparation technique. As RA has been pre-treated, the interfacial zone behaviour of the aggregate with new cement mortar can be enhanced (Alexander, 1996); (Jia, et al, 1986); (Keru and Jianhua, 1988); (Li, et al, 2001); (Popovics, 1987); (Xueqan, et al, 1987) (see Figure 5:, Figure 6 and Figure 7 for the interfacial zone conditions of ReMortar HCl , ReMortar H2SO4 and ReMortar H3PO4 respectively) when compared with that of the normal approach (see Figure 8 for the interfacial zone condition). As the pasteaggregate bond strength increases, the concrete strength also increases (Mindess et al, 2003).…”

Section: Discussionmentioning

confidence: 99%

“…Although reusing RA reduces the consumption of limited resources and thereby saves costs, it also has shortcomings such as weaker interfacial behaviour between aggregate and cement paste, higher portions of cement mortar attached and lower quality (Aitcin and Neville, 1993, Alexander, 1996, Bentz and Garboczi, 1991, Buch et al, 2000, Coventry, 1999, Farran, 1956, Jia et al, 1986, Kawano, 2000, Keru and Jianhua, 1988, Lo, 2000, Mehta and Aitcin, 1990, Mitsui et al, 1994, Mohamed and Hansen, 1999, Olorunsogo and Padayachee, 2002, Popovics, 1987, Ravindrarajah and Tam, 1988, Tasdemir et al, 1998, Tomosawa and Noguchi, 2000, Xueqan et al, 1987. The deformation properties of concrete mixed with secondary aggregate are more than those of concrete mixed with natural gravel.…”

Section: <Table 2> <Table 3>mentioning

confidence: 99%

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Removal of cement mortar remains from recycled aggregate using pre-soaking approaches

Tam

Lê

2007

Resources, Conservation and Recycling

569

165

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With a rising tide of adoption of recycled aggregate (RA) for construction, investigation on ways to improve the quality of RA has been overwhelming. The adoption of RA brings benefits including savings in the limited landfill spaces and the use of natural resources. However, the poorer quality of RA often limits its utilization to low grade applications such as sub-grade activities, filling materials and low grade concrete. The major reason that affects the quality of RA is the large amount of cement mortar remains on the surface of the aggregate, resulting in higher porosity, water absorption rates and thus a weaker interfacial zone between new cement mortar and aggregates, which weakens the strength and mechanical performance of concrete made from RA. This paper attempts to study three pre-soaking treatment approaches; namely ReMortar HCl , ReMortar H2SO4 and ReMortar H3PO4 in reducing the mortar attached to RA. The results show that the behaviour of RA has improved with reduction in water absorption, without simultaneous exceeding the limits of chloride and sulphate compositions after the treatment. This work has also compared the compressive strength, flexural strength and modulus of elasticity of concrete made from the approaches, which shows marked improvements in quality when compared with those using traditional approaches.

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Section: Discussionmentioning

confidence: 99%

Section: <Table 2> <Table 3>mentioning

confidence: 99%

Removal of cement mortar remains from recycled aggregate using pre-soaking approaches

Tam

Lê

2007

Resources, Conservation and Recycling

569

165

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“…He n c e , t h e i n t e r f a c i a l r e g i o n i s g e n e r a l l y r e g a r d e d a s t h e ' we a k l i n k ' i n c o n c r e t e [23][24][25][26][27][28]. In fact, the microscopic structure of RAC is much more complicated than that of normal concrete.…”

Section: Discussionmentioning

confidence: 99%

Diversifying two-stage mixing approach (TSMA) for recycled aggregate concrete: TSMAs and TSMAsc

Tam

2008

Construction and Building Materials

261

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Recycling demolished concrete as recycled aggregate can be applicable to most construction applications. Lower-grade applications, including sub-base and roadwork, have been practicing in many countries; however, higher-grade activities are rarely discussed. This paper develops two mixing approaches by adding silica fume into certain percentages of Recycled Aggregate (RA) in the pre-mix procedure, named as Two-Stage Mixing Approach (silica fume) (TSMA s ) and adding silica fume and proportional amounts of cement into certain percentages of RA in the first mix, named as Two-Stage Mixing Approach (silica fume and cement) (TSMA sc ). Experimentation highlights that improvements have been recorded resulted from the use of various RA percentages from both TSMA s and TSMA sc . The additions of silica fume and proportional cement content in the pre-mix on TSMA s and TSMA sc can fill up the weak areas in the RA and thus develop a stronger interfacial layer around aggregate, and hence a higher strength of the concrete. It, thus, concludes that TSMA s and TSMA sc can provide alternative methodologies for further improvement in quality of this recyclable material.

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“…Some technical problems, including weak interfacial transition zone between cement paste and aggregate, porosity and traverse cracks within demolition concrete, high level of sulphate and chloride contents, impurity, cement attached on RA, poor grading, and high variations in quality, render the use of RA difficult [2][3][4][5][7][8][9][10][11][12][14][15][16][17][18][19][20][21][22][23][24][25][26][27].…”

Section: Obstacles In the Use Of Recycled Aggregatementioning

confidence: 99%

“…Therefore, RAC is "green" concrete. Although reuse of RA reduces the consumption of limited resources and thereby saves costs, they have some shortcomings; for examples, weak interfacial behaviour between aggregate and cement paste, and high portions of cement mortar attached that lower its quality [2][3][4][5][6][7][8][9][10][11][12]. To facilitate the use of RA, it is vital to identify some ways to overcome these shortcomings.…”

Section: Introductionmentioning

confidence: 99%